https://en.wikipedia.org/wiki/Business_cardAspect ratios range from 1.42 to 1.8. There is no standard for the business card dimensions. Sharing dimensions with other cards makes storage easier, for example banking cards (85.60 × 53.98 mm) and business cards in Western Europe (85 × 55 mm) have almost the same size.

Similar to a credit/debit card as most wallets are made to accommodate them, but really your cards can be any size you want - giant, like those cheques that banks present when someone has won a huge sum of money; now they would grab people's attention - though you would need a pretty big card holder, perhaps on wheels lol.